This invention relates to the processing of clay, and in particular, to the dewatering of clay during the processing thereof.
Clays are useful in a variety of applications, such as those where filler materials are desirable. Typically, clays are defined as fine, irregularly shaped crystals of hydrated aluminum silicates. For example, clays are useful in coating applications as taught in U.S. Pat. No. 4,474,860; and as additives as taught in U.S. Pat. No. 4,500,670.
The processing of clays requires that small sized clay particles (e.g., from about 1 .mu.m or less to about 150 .mu.m) be provided in an aqueous medium in order to provide a slurry. The slurry is treated as described in Encyclopedia of Chemical Technology, Vol. 4, p. 62, Interscience, ed. by Kirk-Othmer (1949). After treatment, it is desirable to remove the water from the clay. Typically, the slurry is filtered and the clay is provided in the form of a cake. The dewatered cake is then employed or reslurried for further use.
Unfortunately, the dewatering of clays requires lengthy and costly filtration steps. For example, high molecular weight flocculants can be employed during dewatering processes. Unfortunately, even though rapid dewatering of the clays can be achieved, the amounts of clay solids which are present in the slurries are very low. In addition, low molecular weight dispersants can be employed in order to provide high clay solids containing slurries. Unfortunately, such slurries filter very poorly.
In view of the aforementioned deficiencies, it is highly desirable to provide an improved process for dewatering clays.